Thousands of feet beneath the surface of the ocean, animals live, even thrive, in conditions that are impossible for most of us to even imagine.

Our blue planet is indeed a water planet, yet incredibly, over 90 percent of the ocean remains unexplored and unseen by humans. In a world that’s increasingly tamed and catalogued, it’s astounding to learn that there have been only two journeys to the ocean’s greatest depth, Challenger Deep, off the Mariana Islands—in 1960 and 2012. That first epic descent occurred in 1960…before we’d even ventured into space!

The DEEPSEA CHALLENGER.

At that deepest point, the dark waters of the ocean extend 36,000 feet down—nearly 7 miles. For comparison, the recommended maximum depth for recreational scuba divers is just 130 feet. Photosynthesis is no longer possible at 650 feet, with sunlight gradually diminishing until approximately 3,300 feet, below which, no light ever penetrates.

But far, far down at the bottom of the ocean is an environment unlike any other place on earth. It is frigid—between 30 and 39 degrees Fahrenheit, but never frozen, because salt lowers the freezing point of seawater. The complete darkness is broken only by the light emitted by animals themselves, called bioluminescence. And the intense pressure at these depths is the equivalent of supporting 50 jets on your back!

Obviously, there’s a lot we don’t know about this mysterious region—earth’s largest habitat. Experts believe that up to two-thirds of the plant and animal species in the world ocean may still await our discovery, with as many as one million species of non-bacterial life yet to be identified. In other words, we’ve only scratched the surface.

Most deep-sea creatures are transparent, black, or red, allowing for effective camouflage since red is invisible at these depths. Some, like the bioluminescent lanternfish, send messages to other animals or attract prey via their light-emitting organs. Species like the vampire squid have huge eyes that enable them to use what little light exists, while others have no eyes at all, instead employing smell, touch, and vibration to visualize their surroundings.

A vampire squid. Image via National Geographic.

As a result, many of these creatures are unable to survive the trip up to the surface when collected for research purposes, so scientists who study these marine species now use pressurized containers to replicate their environment.

Increasingly, deep-sea submersibles, both manned and unmanned, are making the long journey to the deep ocean, enhancing our knowledge exponentially with each dive. I, for one, can’t wait to see what they will discover next.